The Rev. John Langan is a professor of philosophy at Georgetown University in Washington, D.C. He wrote the entry “Stem Cell Research and Religious Freedom” for Stem Cell Research: New Frontiers in Science and Ethics.

John Hyde Evans is a sociologist at the University of California, San Diego. He wrote Playing God?: Human Genetic Engineering and the Rationalization of Public Bioethical Debate and The History and Future of Bioethics: A Sociological View.

Michael M. Mendiola was associate professor of Christian ethics for the Graduate Theological Union in Berkeley, Calif. He wrote the article “Human Embryonic Stem Cells: Possible Approaches from a Catholic Perspective” for The Human Embryonic Stem Cell Debate (MIT Press, 2001). Mendiola passed away in 2008.

Dr. Irving Weissman is head of the stem cell research program at Stanford University in Palo Alto, Calif. He opposes an effort to repeal California’s law legalizing embryonic stem cell research.

Jane Maienschein is a professor of history and philosophy of science at Arizona State University in Tempe. She wrote Whose View of Life?: Embryos, Cloning, and Stem Cells (Harvard University Press, 2003).

Ahmad S. Dallal is dean of Georgetown University in Qatar. His research interests include early modern Islamic societies, the causes of 9/11 and the relationship between Islam and science.

Eric M. Woodrum is a professor of sociology and anthropology at North Carolina State University in Raleigh. He has written about the effects of religion and theology on the environmental movement.

Loren Swartzendruber is president of Eastern Mennonite University in Harrisonburg, Va.

Catherine M. Roach is an associate professor women’s studies at the University of Alabama in Tuscaloosa. She is an expert on the spiritual and religious idea of “Mother Nature.”